real analysis - Why is $\ell^\infty (\mathbb {N})$ not separable ...
My functional analysis textbook says "The metric space l∞ l ∞ is not separable." The metric defined between two sequences {a1,a2,a3 …} {a 1, a 2, a 3} and {b1,b2,b3, …} {b 1, b 2, b 3,} is sup i∈N|ai …
functional analysis - $C (X)$ is separable when $X$ is compact ...
Jun 19, 2015 · this result is not trivial: If X is a compact T2 T 2 space X X, then C(X) C (X) is separable iff there is a metric X × X → R X × X → R that induces the topology of X X. You need to use the …
Prove that a subspace of a separable and metric space is itself separable
Prove that a subspace of a separable and metric space is itself separable Ask Question Asked 12 years, 3 months ago Modified 2 months ago
Definition of Separable Space - Mathematics Stack Exchange
Oct 8, 2020 · The standard definition (e.g. from wikipedia) that a separable topological space X X contains a countable, dense subset, or equivalently that there is a sequence (xn) (x n) of points in X …
$X^*$ is separable then $X$ is separable [Proof explanation]
Feb 5, 2020 · $X^*$ is separable then $X$ is separable Proof: Here is my favorite proof, which I think is simpler than both the one suggested by David C. Ullrich and the one I had ...
Is $L^p$ separable? - Mathematics Stack Exchange
Jun 27, 2014 · Wikipedia en.wikipedia.org/wiki/Separable_space#Non-separable_spaces: The Lebesgue spaces Lp, over a separable measure space, are separable for any 1 ≤ p < ∞.
galois theory - The definition of the separable closure of a field ...
Mar 7, 2024 · In any case, each polynomial that has a zero in the separable closure will also decompose in linear factors; thus ext. is normal. Also, note that for some fields such as the rationals or any field …
Prove if $X$ is a compact metric space, then $X$ is separable.
Prove if X X is a compact metric space, then X X is separable. Ask Question Asked 11 years, 3 months ago Modified 6 years, 9 months ago
Every subspace of a separable metric space is separable.
Dec 2, 2017 · IIf it were right it would apply to every separable space because you have not used any of the metric properties. But a separable non-metrizable space can have a non-separable subspace.
Proof of separability of - Mathematics Stack Exchange
A metrizable space is separable if and only if it is second-countable. This means that the euclidean topology on Rn R n has a countable basis. This countable basis is explicitely described in the first …